Tada Kazutoshi, Tanaka Masato, Hanayama Rikinari, Miwa Keiko, Shinohara Azusa, Iwamatsu Akihiro, Nagata Shigekazu
Department of Genetics, Osaka University Medical School, Osaka, Japan.
J Immunol. 2003 Dec 1;171(11):5718-26. doi: 10.4049/jimmunol.171.11.5718.
Apoptotic cells are swiftly phagocytosed by macrophages and immature dendritic cells. In this study, we found that one mouse macrophage cell line (BAM3) engulfed apoptotic thymocytes, but not a lymphoma cell line (WR19L). mAbs that inhibited the phagocytosis of apoptotic thymocytes by BAM3 were identified. Purification of the Ag revealed that it was Src homology 2 domain-bearing protein tyrosine phosphatase substrate-1 (SHPS-1). CD47, the ligand for SHPS-1, was expressed in mouse thymocytes, but not in WR19L. When WR19L was transformed with CD47, the transformants, after induction of apoptosis, could be phagocytosed by BAM3. The WR19L transformants expressing CD47 were more efficiently engulfed in vivo by splenic dendritic cells than the parental WR19L. Masking of the phosphatidylserine exposed on apoptotic thymocytes inhibited the engulfment, whereas the anti-SHPS-1 mAb inhibited not only the engulfment, but also the binding of apoptotic cells to phagocytes. These results indicate that macrophages require CD47 and phosphatidylserine on apoptotic cells for engulfment, and suggest that the interaction between CD47 and SHPS-1 works as a tethering step in the phagocytosis.
凋亡细胞会迅速被巨噬细胞和未成熟树突状细胞吞噬。在本研究中，我们发现一种小鼠巨噬细胞系（BAM3）能吞噬凋亡胸腺细胞，但不能吞噬淋巴瘤细胞系（WR19L）。我们鉴定出了抑制BAM3对凋亡胸腺细胞吞噬作用的单克隆抗体。对该抗原进行纯化后发现它是含Src同源2结构域的蛋白酪氨酸磷酸酶底物-1（SHPS-1）。SHPS-1的配体CD47在小鼠胸腺细胞中表达，但在WR19L中不表达。当WR19L用CD47进行转化后，诱导凋亡后的转化体能够被BAM3吞噬。表达CD47的WR19L转化体在体内比亲本WR19L更易被脾树突状细胞吞噬。掩盖凋亡胸腺细胞上暴露的磷脂酰丝氨酸会抑制吞噬作用，而抗SHPS-1单克隆抗体不仅抑制吞噬作用，还抑制凋亡细胞与吞噬细胞的结合。这些结果表明巨噬细胞吞噬凋亡细胞需要凋亡细胞上的CD47和磷脂酰丝氨酸，并提示CD47与SHPS-1之间的相互作用在吞噬作用中起拴系步骤的作用。
